Self supporting shadow mask with reinforcing ribs and gusset plates for colored television picture tubes

ABSTRACT

A shadow mask for colored TV picture tubes has a front section, containing the conventional foraminous or translucent area formed by a multitude of miniature apertures through which electron beams pass from the electron guns at the rear of the tube to the viewing face at the front of the tube; an imperforate margin area around the translucent area; a rearward extending wall from the edge of the margin area; and an inward directed flange formed along the rear edge of the wall. The flange contains a plurality of strengthening fragmentary gusset plate members.   D R A W I N G

United States Patent [72] Inventor Myron C. Kirchner Itasca, Ill.

[21] Appl. No. 821,056 [22] Filed 313/85X 3l3/85X 313/85X May 1, 1969Patented Jan. 26, 1971 11/1969 Mears....

[73] Assignee Northern Metal Products, Inc.

Franklin Park, III.

a corporation of Delaware Assistant Examiner-V. LafranchiAttorney-Stryker and Jacobson ABSTRACT: A shadow mask for colored TVpicture tubes foraminous or translucent area formed by a multitude ofminiature through which electron beams [54] SELF SUPPORTING SHADOW MASKWITH has a front section, containing the conventional REINFORCING RIBSAND GUSSET PLATES FOR COLORED TELEVISION PICTURE TUBES Figs aperturespass from the electron guns at the rear of the tube to the viewing faceat the front of the tube;

. 313/85, an imperforate margin area around the translucent area; a

3 13/286, 313/348 rearward extending wall from the edge of the marginarea; and H0lj 29/46 an inward directed flange formed along the rearedge of the wall ty of strengthening fragmen- 4 Claims, 3 Drawing [52][51] Int. Cl.......

. The flange contains a plurali [50] Field of Search.

928 tary gusset plate members.

PATENTEB JAN 25 191i 'Hllh.

"Hill" INVENTOR MYRO/V BY W M ATTOIQNEYS SELF SUPPORTING SHADOW MASKWITH REINFORCING RIBS AND GUSSET PLATES FOR COLORED TELEVISION PICTURETUBES BACKGROUND OF THE INVENTION 1. Field of the Invention Thisinvention is used in the construction of colored TV picture tubescontaining aperture or shadow masks and is principally directed towardproviding a mask which is essentially self-supporting.

2. Description of the Prior Art Heretofore, for the most part, thepractice has been to take aconventional shadow mask, which has itstranslucent area shaped to conform to the front face of the picturetube, attach it to a heavy mounting ring to form a complete assembly,and then mount the entire assembly in some convenient fashion to theinside of the glass bulb of the picture tube. The mounting ring helps tophysically stabilize the mask but it and its associated hardwareconstitutes a sizeable portion of the mask assembly. This results in amask assembly that is costly, heavy, and somewhat unstable because oftemperature differentials during a long warmup period while the assemblyapproaches a uniform steady temperature level. This has produced somewarping or twisting of the face of the mask which, in turn, adverselyaffects the registration of the mask apertures with respect to thephosphor dots on the face of a picture tube. Attempts have been made toeliminate or modify this traditional mounting ring assembly. Typical ofthis is the shadow mask described in US. Pat. No. 3,376,451 and thatdescribed in copending application Ser. No. 822,792 filed Apr. 2, I969by the present applicant.

SUMMARY I The present invention is somewhat of a variation ormodification of the aperture mask described in the aforementionedcopending application. The mask contains the conventional translucentarea surrounded by an imperforate marginal area, has a rearwardextending imperforate wall and an inward extending flange at the rearedge of the wall. Numerous strengthening ribs are in the variousimperforate sections to assist in providing enough strength to make themask self supporting. Fragmentary gusset plate members are welded atstrategic locations on the flange to provide additional strengtheningwhile keeping the weight and mass of the mask at a minimum. A mask ofthis nature not only warms up to uniform operating temperature quicklybut also is rigid enough to withstand normal handling without anysignificant shift in the location of the tiny apertures. Masks of thisnature can be attached to the glass bulb by springlike mounting tabslocated on the wall section and containing openings for mating withmounting studs in the glass bulb.

BRIEF DESCRIPTION OF THE DRAWINGS F IG. 1 is a rear view of a shadowmask for a colored TV picture tube constructed according to theteachings of this invention;

FIG. 2 is a side view of the shadow mask; and

FIG. 3 is a sectional view taken along viewing line 3-3 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The aperture or shadow maskcontains the conventional foraminous or translucent area formed by amyriad of apertures which are usually chemically milled through a thinsheet of metal, such as stainless steel. In normal use, when made partof the final picture tube assembly, the translucent section 10 of theshadow mask is located near and facing the front viewing face to of thepicture tube and is between the viewing face and electron guns at therear of the tube. When the tube is in operation, the electron beams aredirected through the translucent area 10 to impinge upon coloredphosphor dots on the inside of the face of the picture tube. The shadowmask is also used during the process of laying down the colored phosphordots in conventional triad patterns. Without delving into this processto any great degree, it should be pointed out that during the process offorming the phosphor dots the mask ordinarily is removed andrepositioned with respect to the face of the picture tube a number oftimes so it is important that the mask be stable enough so that the tinyapertures return virtually to their same previous location each time themask it is temporarily removed and reinserted. It should also beapparent that the mask should be temperature stable so that theminiature apertures in the translucent area do not shift with respect tothe phosphor dots on the industry face plate to interfere with thepassage of the electron beams directed toward the face plate.

Conventionally, the translucent area 10 is partially domed or curved,usually aspherically, to conform to the shape of the inner face of thepicture tube. Various methods, procedures and equipments have beendeveloped and are used today throughout the industry for etching out thetranslucent areas and for doming or curving the mask face as desired.These methods, procedures and equipments are not considered part of thepresent invention.

Surrounding the translucent area 10 is a marginal imperforate area 11which is merely an extension of the same sheet of metal from which thetranslucent area is formed. In marginal area 11, near the outer edge ofthe translucent area 10, there is formed a continuous, inwardprojectingshallow groove 12 which serves as a strengthening rib for the frontportion of the aperture mask. Ordinarily, this rib is formed in a pressusing standard well-known techniques. At the outer edge of the marginalarea 11 the metal sheet bends rearward to form an imperforated wallsection 13 which extends completely around the front portion of themask. The depth of the wall section 13, Le. its dimension from front toback, may vary from mask to mask depending upon a number of factorsineluding, but not limited to, the size an and the type of the picturetube for which the mask is being made. However, in general terms, themask is referred to as being deep-drawn as differentiated from ashallow-drawn mask which has a very short wall section. Typically, withno limitation intended, the wall may be in the order of l inches deepfor an aperture mask used in a 21 or 24 inch picture tube. A shallow,inwardly directed groove 14 which extends continuously around wall 13provides a strengthening rib for the wall section. The location and sizeof strengthening rib 14 depends on a number of factors including thesize of the mask, the dimension of the wall, the metal thickness, etc.This choice can be and ordinarily is made by the skilled artisandepending on the various factors and no precise formula for covering thevarious conditions appears to be reasonably predeterminable. In someinstances, it has been found that additional strengthening ribs may bedesirable. These may be the same as and run parallel to rib 14 or theymay meander over the wall section 13.

At the rear edge of wall l3 the metal sheet bends inward to form flange16 in a plane which is substantially at to the central axis of theaperture mask. The dimension of flange I6 also depends on a number ofdifferent factors but suffice is to point out that it should not extendinward so far as to interfere with the passage of the electron beamsfrom the electron guns to the viewing face of the tube. The inner edgeof flange 16 may be flared angularly as illustrated at 18, to providesome degree of shielding. As shown in FIG. 1, flange I6 is in arectangular geometric form corresponding in general with the geometricform of the aperture mask for use with a rectangular picture tube.Attached securely to the four corners of flange 16 are reinforcinggusset plate members 19. Preferably, the gusset plate members areattached by welding them to the flange. Also, preferably, the gussetplates 19 are made out of the same type of metal as the rest of the maskand dimensionally may be the same thickness as the metal sheet fromwhich the mask is formed. However, it has been found preferable that thegusset plate members 19 be in the order of twice the thickness of theflange material. Although it has been found that in most instances thecorner-located gusset plate members 19 provide sufficient strengtheningfor the desired results, in some instances it may be necessary ordesirable to enhance the strength of the mask by welding additionalgirsset plate members at suitable locations between corner gussetmembers. Typically, fragments of metal similar to gusset plate members19 may be welded to flange 16 at the center of each of the sides of theflange. The sizes of these additional gusset plate members may beselected according to the degree of additional strength desired whilekeeping in mind the necessity of keeping the mass and the weight of themask structure at a minimum.

Directing attention back to FIG. 2, wall 13 may be provided withadditional strengthening and supporting ribs 23 which run across thecontinuous rib 14. The number. dimensions and the spacing of these crossribs 23 again is a matter of choice depending on a number of factors andcan be selected by the artisan familiar with construction of masks ofthis nature. Attached to the outside of wall 13 are springlike mountingtabs 20 which contains openings 21 on tongue portions 22 for mating withpins (not shown) extending out from the glass bulb of the picture tube.Because of the inherent strength of the mask brought about by thesupporting ribs in conjunction with the suitably located gusset platemembers, it can be used in the phosphor dot forming process and bemounted as part of the final assembly of a the picture tube and remainsecure in this virtually self-supporting manner without the need of theusual heavy, rigid supporting rings and mounts which had beencommonplace heretofore.

I claim:

1. A self-supporting shadow mask for a colored television picture tubecomprising: a thin metal sheet having a front section containing atranslucent area defined by a myriad of miniature apertures through themetal sheet and an imperforate margin area surrounding the translucentarea with a continuous strengthening rib formed in said margin area, animperforate wall section extending rearward from the edge of said fromsection, said wall section containing strengthening ribs formed therein,a flange section directed inwardly from the back edge of said wallsection, said flange section being generally rectangular in shape; andfragmentary gusset plate members rigidly attached to said flange sectionat its four corners.

2. The invention as described in claim 1 further including furtherfragmentary gusset plate members rigidly attached to a said flange atlocations between the corner gusset plate members.

3. The invention as in claim 1 wherein the front section, the wallsection and the flange section are all formed from a single sheet ofmetal.

4. The invention as in claim 3 wherein the gusset plate members are madefrom metal having the same characteristics as the mask metal and rangeup to three times its thickness, said gusset plate members being weldedto the flange section.

1. A self-supporting shadow mask for a colored television picture tubecomprising: a thin metal sheet having a front section containing atranslucent area defined by a myriad of miniature apertures through themetal sheet and an imperforate margin area surrounding the translucentarea with a continuous strengthening rib formed in said margin area, animperforate wall section extending rearward from the edge of said frontsection, said wall section containing strengthening ribs formed therein,a flange section directed inwardly from the back edge of said wallsection, said flange section being generally rectangular in shape; andfragmentary gusset plate members rigidly attached to said flange sectionat its four corners.
 2. The invention as described in claim 1 furtherincluding further fragmentary gusset plate members rigidly attached to asaid flange at locations between the corner gusset plate members.
 3. Theinvention as in claim 1 wherein the front section, the wall section andthe flange section are all formed from a single sheet of metal.
 4. Theinvention as in claim 3 wherein the gusset plate members are made frommetal having the sAme characteristics as the mask metal and range up tothree times its thickness, said gusset plate members being welded to theflange section.